why proper not returning error when can't produce enough satisfies instances?

[andrzejsliwa]

why proper not returning error when can't produce enough satisfies instances?

I mean in proper:module, proper:check_spec, proper:check_specs...

I have just [] ... as result of (proper:check_specs(example):

Testing example:size/1
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Error: Couldn't produce an instance that satisfies all strict constraints after 50 tries.

Testing example:is_empty/1
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Error: Couldn't produce an instance that satisfies all strict constraints after 50 tries.

Testing example:new/0
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OK: Passed 200 test(s).

Testing example:safe_pop/1
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Error: Couldn't produce an instance that satisfies all strict constraints after 50 tries.

Testing example:pop/1
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OK: Passed 200 test(s).

Testing example:push/2
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Error: Couldn't produce an instance that satisfies all strict constraints after 50 tries.

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